frp-rc design - part 3b · 6 bfrp-rc design - part 3, (50 min.) this session continues with basalt...
TRANSCRIPT
FRP-RC Design - Part 3b
Steve Nolan
2019
2Professor Brahim Benmokrane, University of Sherbrooke, Quebec, CANADA
Promoting & connecting the Australian Composites Industry – Brisbane, Qld
Composites Australia, December 5, 2018
Design of concrete structures internally reinforced with FRP bars
Canada Research Chair in Advanced Composite Materials for Civil Structures
NSERC/Industrial Research Chair in Innovative FRP Reinforcement for Concrete
Director, The University of Sherbrooke Research Centre on FRP Composites
Department of Civil Engineering
University of Sherbrooke, Sherbrooke, QC, Canada
E-mail:[email protected]
Adapted from…
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Fiber-reinforced polymer (FRP) materials have emerged as analternative for producing reinforcing bars for concrete structures.Due to other differences in the physical and mechanical behaviorof FRP materials versus steel, unique guidance on theengineering and construction of concrete structures reinforcedwith FRP bars is necessary.
Course Description
1
4
• Understand the mechanical properties of FRP bars
• Describe the behavior of FRP bars
• Describe the design assumptions
• Describe the flexural/shear/compression design procedures of
concrete members internally reinforced with FRP bars
• Describe the use of internal FRP bars for serviceability &
durability design including long-term deflection
• Review the procedure for determining the development and
splice length of FRP bars.
Learning Objectives
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FRP-RC Design - Part 1, (50 min.)
This session will introduce concepts for reinforced concrete design with FRP rebar. Topics will
address:
• Recent developments and applications
• Different bar and fiber types;
• Design and construction resources;
• Standards and policies;
FRP-RC Design - Part 2, (50 min.)
This session will introduce Basalt FRP rebar that is being standardized under FHWA funded project
STIC-0004-00A with extended FDOT research under BE694, and provide training on the flexural
design of beams, slabs, and columns for:
• Design Assumptions and Material Properties
• Ultimate capacity and rebar development length under strength limit states;
• Crack width, sustained load resistance, and deflection under service limit state;
Content of the Course
6
BFRP-RC Design - Part 3, (50 min.)
This session continues with Basalt FRP rebar from Part II, covering shear and axial design of
columns at the strength limit states for:
• Ultimate capacity – Flexural behavior (Session 3a);
• Shear resistance of beams and slabs (Session 3b);
• Fatigue resistance under the Fatigue limit state
• Axial Resistance of columns;
• Combined axial and flexure loading.
FRP-RC Design - Part IV (Not included at FTS - for future training):
This session continues with FRP rebar from Part III, covering detailing and plans preparation:
• Minimum Shrinkage and Temperature Reinforcing
• Bar Bends and Splicing
• Reinforcing Bar Lists
• General Notes & Specifications
Content of the Seminar
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Session 4: (1:30 pm - 2:30 pm)
Shear behaviour
• - Design philosophy
• - Shear strength
• - Design examples
Session 3b: Shear Behavior
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400
200
0
600
1200
1000
800
1400
1800
1600
0.0 0.5 1.0 2.0 2.5 3.01.5
Strain (%)
Str
es
s(M
Pa
)
Carbon FRP
Aramid FRP
Glass FRP
Steel
Stress-Strain Relationships for FRP Bars
Session 3b: Shear Behavior
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Shear Strength of FRP Reinforced Members
• FRP has a relatively low modulus of elasticity
• FRP has a high tensile strength and no yielding point
• Tensile strength of a bent portion of an FRP bar is
significantly lower than a straight portion
• FRP has low dowel resistance
Session 3b: Shear Behavior
10
Shear Strength of FRP Reinforced Members
• Concrete reinforced with FRP has a lower shear strength than concrete with steel reinforcement
• Increased crack width
• Small compressive
zone depth
→ Less aggregate interlocking
→ Less concrete resistance in
the zone compressive
3
Session 3b: Shear Behavior
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Most of the design codes and design guidelines recommend the following simplified approach for shear design:
Vn = Vcf + Vsf + Vp
where
Vn = nominal shear strength
Vcf = concrete contribution to shear strength
Vsf = shear reinforcement contribution to shear strength
Vp = prestressing resisting component
Session 3b: Shear Behavior
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Shear transfer mechanism in a cracked
(1) Uncracked
concrete
Applied Load
(3) Arching
action(2) Aggregate
interlock
(4) Residual tensile
stresses
(6) Shear reinforcement
(5) Dowel action
Session 3b: Shear Behavior
13Diagonal tension failure mode
Beam CN-3 Beam GN-3
Shear Behaviour of FRP RC Beams
Session 3b: Shear Behavior
14Size Effect
Session 3b: Shear Behavior
15
Beam B1-1 Beam B1-2
Diagonal Tension Failure Mode
Session 3b: Shear Behavior
16Shear Failure of SC-9.5-2 (CFRP @ d/2)
Shear Behaviour of Concrete Bridge Girders Reinforced with FRP
Stirrups (T-Section) – MTQ Research Project (2007-2009)
17Reinforcing Cage and Concrete Casting
Shear Behaviour of Concrete Bridge Girders Reinforced with FRP
Stirrups (T-Section) – MTQ Research Project (2007-2009)
18Curing and transportation
Shear Behaviour of Concrete Bridge Girders Reinforced with FRP
Stirrups (T-Section) – MTQ Research Project (2007-2009)
19GFRP-Cages
Shear Behaviour of FRP RC Beams
Session 3b: Shear Behavior
20CFRP Stirrups
Shear Behaviour of FRP RC Beams; GFRP & CFRP
Stirrups
Session 3b: Shear Behavior
21Shear Failure of SC-9.5-3 (CFRP @ d/3)
Shear Behaviour of Concrete Bridge Girders Reinforced with FRP
Stirrups (T-Section) – MTQ Research Project (2007-2009)
22Shear Failure of SS-9.5-2 (Steel @ d/2)
Shear Behaviour of Concrete Bridge Girders Reinforced with FRP
Stirrups (T-Section) – MTQ Research Project (2007-2009)
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416
536
440
376
272300
400
500
600
200
100
0
SS-9.5-2 SC-9.5-2 SC-9.5-3 SC-9.5-4 SG-9.5-2 SG-9.5-3 SG-9.5-4
Fail
ure
Sh
ea
r L
oa
d(k
N)
38%62%
97%
259
5%
24%
337 53%
Shear Capacity
Shear Behaviour of Concrete Bridge Girders Reinforced with FRP
Stirrups (T-Section) – MTQ Research Project (2007-2009)
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Shear design is similar to the simplified method of CSA A23.3-14, i.e.
Vr ≥ Vc + Vs,F
Vc accounts for
• Shear resistance of uncracked concrete
• Aggregate interlock
• Dowel action of the longitudinal reinforcement
• Arching action
Vs,F = Shear carried by the FRP shear reinforcement
Session 3b: Shear Design (CSA-S806)
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• However, Vr shall not exceed
' dc f
r ,max c c w v p
M V
M
V 0,22 f b d 0,5V
• For FRP Stirrups
Vr VcVs,F
• For Steel Stirrups
Vr VcVs,F
Session 3b: Shear Design (CSA-S806)
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If the member effective depth does not exceed 300 mm and there is no axial load:
1/3
)1/3
c m r
'
c w v
f
m
f
f b dc
where
V d
M
k kV 0.05
k 1
kr 1 (EFFw
BUT
c c c w vf ' b dV 0.11
c w vf ' b dVc 0.22c
cf ' 60MPa
or if the member effective depth exceeds 300 mm and transverse
shear reinforcements are equal or greater to Av,min (Clause 8.4.4.8)
Session 3b: Shear Design (CSA-S806)
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To account for size effect, for sections with an effective
depth greater than 300mm and with less transverse
reinforcement than Av,min
1/3
750
c m r s
'
c w v
s
f b dc
where
k k kV 0.05
k 1450 d
Session 3b: Shear Design (CSA-S806)
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• Shear Carried by Transverse Reinforcement
• For Members with FRP Transverse Reinforcement
• For Members with Steel Transverse Reinforcement
s,FV
s
0.4F AFv fFu dv cot
s,s s
V S Av f ydv cot
fFu shall not be greater than 0.005EF
Session 3b: Shear Design (CSA-S806)
29
• Minimum Shear Reinforcement
• A minimum area of shear reinforcement shall be provided in all regions of flexural members where
Vf > 0.5Vc+ ΦFVp, or Tf > 0.5Tcr.
This requirement may be waived for:•Slabs and footings
•Concrete joist construction
•Beams with total depth not greater than 250 mm
•Beams cast integrally with slabs where overall depth is not greater than
one-half the width of the web or 600 mm.
Session 3b: Shear Design (CSA-S806)
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• Minimum Shear Reinforcement
• The minimum are of FRP shear reinforcement shall be such that
vF c
Fu
bwsf '
0.4 fA 0.07
fFu shall not be greater than 1200MPa or 0.005EF.
Session 3b: Shear Design (CSA-S806)
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Session 3b: Shear Design (CSA-S806)
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Session 3b: Shear Design (CSA-S806)
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Session 3b: Shear Design (CSA-S806)
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Session 3b: Shear Design (CSA-S806)
35
Session 3b: Shear Design (CSA-S806)
3629Professor Brahim Benmokrane, University of
Sherbrooke, Quebec, CANADACan ada
Session 3b: Shear Design Example (CSA-S806)
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Session 3b: Shear Design Example (CSA-S806)
38
Session 3b: Shear Design Example (CSA-S806)
39
Session 3b: Shear Design Example (CSA-S806)
40
Session 3b: Shear Design Example (CSA-S806)
41
Session 3b: Shear Design Example (CSA-S806)
42
Session 3b: Shear Design Example (CSA-S806)
43
Session 3b: Shear Design Example (CSA-S806)
44
Session 3b: Shear Design Example (CSA-S806)
45
Session 3b: Shear Design Example (CSA-S806)
46
Additional Shear Design of Beam
Reinforced with GFRP Bars
According to CSA S806-12
Session 3b: Shear Design Example (CSA-S806)
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Loads:• Dead load (D.L) = 85 kN/m
• Live load (L.L) = 40 kN/m
Service limit state (Ws.l.s) = 85 + 40 = 125 kN/m
Ultimate limit state (Wu.l.s) = 1.25 * 85 + 1.5 * 40 = 166.25 kN/m
S.L.S U.L.S
V = W L / 2 (kN) 437.50 581.88
M = W L2 / 8
(kN.m)
765.63 1018.28
Session 3b: Shear Design Example (CSA-S806)
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Session 3b: Shear Design Example (CSA-S806)
49
Session 3b: Shear Design Example (CSA-S806)
50
Design Steps
• Design for shear force
❖ Calculate concrete contribution.
❖ Calculate GFRP stirrups contribution
Session 3b: Shear Design Example (CSA-S806)
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Session 3b: Shear Design Example (CSA-S806)
52
Session 3b: Shear Design Example (CSA-S806)
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Session 3b: Shear Design Example (CSA-S806)
54
Session 3b: Shear Design Example (CSA-S806)
55
Session 3b: Shear Design Example (CSA-S806)
56
End of Session
Session 1: Introduction
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Questions
Raphael Kampmann PhDFAMU-FSU College of Engineering
Tallahassee, FL.
Chase Knight, Ph.D, P.E.
State Materials Office,
Gainesville, FL.
Steven Nolan, P.E.FDOT State Structures Design Office,
Tallahassee, FL.
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Marco Rossini, PhD studentUniversity of Miami.
Coral Gables, FL.